mysql表结构表空间和索引的查

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mysql表结构表空间和索引的查询

1.查询表的结构信息
Sql代码  
desc tableName;  

show columns from tableName;  

describe tableName  
  上面的结果返回的结果是一样的。
2 查询表的列信息。
Sql代码  
select * from   
information_schema.columns   
where table_name='tableName';  
3 查看库中所有的库
Sql代码  
SELECT LOWER(schema_name) schema_name  
FROM  
information_schema.schemata  
WHERE  
schema_name NOT IN (  
'mysql',  
'information_schema',  
'test'  
)  
4 查询某个库中所有的表
Sql代码  
SELECT table_name, create_time updated_at, table_type, ENGINE, table_rows num_rows, table_comment, CEIL(data_length / 1024 / 1024) store_capacity  
FROM  
information_schema.TABLES  
WHERE table_schema = 'schema_name' AND table_name NOT LIKE 'tmp#_%' ESCAPE '#'  
5 查看某一个库下某一个表的所有字段
Sql代码  
SELECT  
    lower(column_name) column_name,  
    ordinal_position position,  
    column_default dafault_value,  
    substring(is_nullable, 1, 1) nullable,  
    column_type data_type,  
    column_comment,  
    character_maximum_length data_length,  
    numeric_precision data_precision,  
    numeric_scale data_scale  
FROM  
    information_schema.COLUMNS  
WHERE  
    table_schema = 'admin_portal'  
AND table_name = 'ap_epiboly_task';  

6  查看某一个库下某一张表的索引

Sql代码  
<strong>SELECT DISTINCT  
    lower(index_name) index_name,  
    lower(index_type) type  
FROM  
    information_schema.statistics  
WHERE  
    table_schema = 'employees'  
AND table_name = 'employees';</strong>  
7 查看某一个库下某一个表的注释

Sql代码  
SELECT  
    table_comment comments  
FROM  
    information_schema.TABLES  
WHERE  
    table_schema = 'employees'  
AND table_name = 'employees';  
8

1.查看索引

（1）单位是GB

SELECT CONCAT(ROUND(SUM(index_length)/(1024*1024*1024), 2), ' GB') AS 'Total Index Size' FROM information_schema.TABLES WHERE table_schema LIKE 'test';
+------------------+
| Total Index Size |
+------------------+
| 1.70 GB |
+------------------+

（2）单位是MB

SELECT CONCAT(ROUND(SUM(index_length)/(1024*1024), 2), ' MB') AS 'Total Index Size' FROM information_schema.TABLES WHERE table_schema LIKE 'test';

   其中“database”为你所要查看的数据库

2.查看表空间

SELECT CONCAT(ROUND(SUM(data_length)/(1024*1024*1024), 2), ' GB') AS 'Total Data Size'
FROM information_schema.TABLES WHERE table_schema LIKE 'test';
+-----------------+
| Total Data Size |
+-----------------+
| 3.01 GB |
+-----------------+

3.查看数据库中所有表的信息
SELECT CONCAT(table_schema,'.',table_name) AS 'Table Name',
CONCAT(ROUND(table_rows/1000000,2),'M') AS 'Number of Rows',
CONCAT(ROUND(data_length/(1024*1024*1024),2),'G') AS 'Data Size',
CONCAT(ROUND(index_length/(1024*1024*1024),2),'G') AS 'Index Size' ,
CONCAT(ROUND((data_length+index_length)/(1024*1024*1024),2),'G') AS'Total'FROM information_schema.TABLES WHERE table_schema LIKE 'test';